When you first encounter terns, their mid-air, hairpin turns seem unpredictable and difficult to capture — especially since these birds are quite small when you’re thinking about filling the frame. One one level they are tough to photograph. Terns rise and fall, juke left and right in minute movements that make autofocus with a tele-zoom a little tricky. The number of photos I have without perfect eye focus attests to that — and to the limitations of my budget lens.

Once you watch them long enough, though, you realize there is, indeed, a method to their flying madness. And generally, even as they zig zag out of lens range, they tend to return and scope out the same fishing grounds for at least a few passes before they move on.

This Forster’s Tern was doing loops over the flooded marsh at Coyote Hills. In the time I was there, his efforts yielded one small fish . . . visible in this grainy crop, shot too far out of my range.